In the quantitative inheritance of finger-ridge counts, it is conventional to take the largest of the ulnar and radial ridgecounts as a measure of the pattern size. In the case of a loop, there is but one measurement, a radial count on an ulnar loop, and an ulnar count on a radial loop. In a whorl there are (usually) two counts, and it is in this instance when the convention is used. In the case of an arch, both ulnar and radial counts are zero.